ABSTRACT
p21ras belongs to the family of GTPases, that cycle between an active GTP-bound state and an inactive GDP-bound state. This family includes, among others, the α-subunit of heterotrimeric G proteins, initiation and elongation factors of protein synthesis, and a large number of small GTPases. Analogous to the pathway in which the heterotrimeric G proteins functions, the “p21ras pathway” can be divided into an upstream and a downstream part, taking the GTP/GDP switch as a reference point. All events that are directed to activate p21ras (the dissociation of GDP or the inhibition of GTP hydrolysis) are considered to be upstream elements of the ras pathway and all cellular events that result from p21ras activation are considered to be downstream elements.
